stoke's law
DESCRIPTION
Stoke's Law calculates rate of destabilization of an emulsion by equating gravitational force with the opposing hydrodynamic force. Stoke's Law can be used to predict emulsion stability.TRANSCRIPT
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Stoke’s Law
Photo courtesy of Patrick Willems on Flickr
Prof. Abd Karim Alias Universiti Sains Malaysia
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Stoke's Law calculates rate of destabilization of an emulsion by equating gravitational force with the opposing hydrodynamic force:
where V = velocity of separation (or rate of creaming), cm/sec; g = acceleration of gravity (980 cm/sec); r = droplet radius (cm); d1 = density of disperse phase (g/cm3); d2 = density of continuous phase (g/cm3); µ = viscosity of the continuous phase (g/cm.sec) (µ = 0.01 at 20 °C)
Stoke’s Law
2gr2 (d1 – d2)
9µ
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You are making orange soda from an orange flavor emulsion. The density of the orange oil is 0.85 g/cm3, the density of a 10% sugar solution is 1.04 g/cm3, the average particle radius is 3.0 micron, and µ = 0.01 g/cm·sec. What is V? Will the emulsion remain stable?
Stoke’s Law
PROBLEM 1
2gr2 (d1 – d2)
9µ
Photo courtesy of Brent Moore on Flickr
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You homogenize the beverage mix so that the particle radius is decreased to 0.3 micron. What is V? Will the emulsion remain stable?
Stoke’s Law
PROBLEM 2
2gr2 (d1 – d2)
9µ
Photo courtesy of Brent Moore on Flickr
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You add brominated vegetable oil to the orange oil so the overall density is 0.95 g/cm3 . What is V for particle radius 3.0 micron? For 0.3 micron? Will the emulsion remain stable?
Stoke’s Law
PROBLEM 3
2gr2 (d1 – d2)
9µ
Photo courtesy of Brent Moore on Flickr
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For the above problems, which approach stabilized the emulsion more -- decreasing particle size or increasing density of the dispersed phase?
Stoke’s Law
PROBLEM 4
2gr2 (d1 – d2)
9µ
Photo courtesy of Brent Moore on Flickr